Home › Forums › Coking › Design and Reliability › Cokedrums, Structure, Inspection › Drums › Drum ovh lines cleanout facilities › RE: Drum ovh lines cleanout facilities
Clean out facilities are typically full line size Blind Tees/Crosses or removable Ells.
Tees or crosses provide full access to the pipe and may facilitate and faster the cleaning process, but are also more costly. It is highly recommended in the first turn coming out of the drum, which requires frequent cleanout during normal operation. In the other hand, they also add extra turbulence in the lines, adding pressure drop, and possibly even areas where coke buildup is enhanced, which may make it necessary to clean out the lines more often, so its excessive use should avoided as possible. The pressure drop increase will have a long-term effect in the process, so every 1 psi increase reduces liquid yield. My recollection is that liquid yield is reduced about 0.15% per 1 psi increase; although it looks a small number, it becomes a significant loss opportunity.
Ells are cheaper and provides easy access in both directions; the rigging to handle an ell would be similar to that needed for a blind flange, but slightly more robust. The ells could have welded lifting lugs installed to make the rigging a snap. Ells provide lower pressure drop and avoid coke deposition areas. It can be considered for sections where the timeframe required to perform the cleaning will not have any effect in the normal operating cycle, because the pair of drum would have to be out of service to perform any work; like, sections of the pipe between the common valve (SP3) to the Fractionator.